For over 1,500 years, Japan and Korea had gone through cultural exchange, trade, war, and political contact which underlies their relations even today. During the ancient era, exchange of culture and ideas between Japan and Asia were common through migration via the Korean Peninsula or diplomatic contact and trade between Japan and Korea. Cultivation of rice, Buddhism, Chinese foods, Chinese characters and other technology came to Japan via Korea.[1]

In a modern context, Japan–Korearelations pertain to three states: Japan, North Korea, and South Korea. Historically, Japan and Korea have had cultural interactions for more than 1,500 years and had direct political contact for almost as long. Korea became Japan's territory as a result of the Japan-Korea Annexation Treaty which was signed in 1910. When Japan was defeated in World War II, U.S. Army Forces proclaimed the occupation and administration of Korea. South Korea has been independent as of August 15, 1945, and North Korea became independent on September 9 of the same year.

Bilaterally and through the Six-Party Talks, North Korea and Japan continue to discuss the case of Japanese citizens abducted by the North Korean government during the 1970s and 1980s, although there are no diplomatic relations between the two; Japan does not recognize North Korea as a sovereign state.

The last king of Baekje, Uija, formed an alliance with Japan and made Prince Buyeo Pung and King Zenko stay there as their hostages. In 660, Baekje fell when it was attacked by Silla and the Tang Dynasty China. Former generals of Baekje, including Gwisil Boksin, asked Japan to return Prince Buyeo Pung and to provide military aid. In 663, Japan, supporting Baekje, was defeated by the allied forces of Tang dynasty China and Silla in Korean Peninsula (the Battle of Baekgang), and the restoration of Baekje ended up in failure. After the fall of Baekje, Japan took in many Korean refugees, but at the same time hostility between Japan and Silla escalated. Empress Jitō honored King Zenko by giving him the hereditary title of Kudara no Konikishi and allowed him to pass on his royal lineage to future generations. According to the Shoku Nihongi(続日本紀?), Takano no Niigasa, background of the naturalized clansmen Yamato-no-Fumito(和史?), was a 10th-generation descendant of King Muryeong of Baekje who was chosen as a concubine for Emperor Kōnin and subsequently became the mother of Emperor Kammu.[4][5]

Chinese culture was introduced to Japan via the Korean Peninsula, but the Korean value slumped when Chinese culture was introduced directly by Japanese missions to Tang China. Emperor Kammu severed diplomatic relations with Silla in 799.[6] From the early 9th–11th centuries, Korean pirates plundered the north Kyushu region of Japan and Japan-Korea relations deteriorated.[7][8]

During the middle Kamakura period, Japan suffered from the Mongol Empire (Yuan Dynasty), which was then dominant on the continent, and its subject kingdom, the Goryeo of Korea. The History of Yuan states that the Mongol invasions of Japan began with King Chungnyeol of Goryeo "persistently recommending an expedition to the east to Yuan's emperor in order to force Japan to become its subject."[9] In order to invade Japan, the Mongols ordered the Korean king to manufacture 1000 warships.[10] The two Mongol - Korean fleets were destroyed by storms, giving rise to the myth of the Kamikaze, the divine wind that protected Japan. At the time of Mongol invasions of Japan, Japanese people were scared by the attacks of the Mongol and Goryeo army, saying, 'moko kokuri no oni ga kuru (the devils of the Mongol and Goryeo will come)', which phrase later came to represent something scary; thus a tradition spread to the whole country to scare children by saying 'mukuri kokuri, oni ga kuru' to make them behave themselves.

In 1592 and 1598 Toyotomi Hideyoshi, who had unified the nation, ordered 'daimyo' (feudal lords) all over the country to the conquest of Ming Dynasty China by way of Korea, after the latter's refusal to allow Japanese forces to march through. Japan completed the occupation of the Korean peninsula in three months. The Korean king Seonjo fled to China and asked Ming for help. The Chinese emperor sent his army and recaptured the Korean peninsula. However, the Japanese military gathered in Seoul and counterattacked China. Amid the stagnation of the battle between the Ming army and the Japanese army, Hideyoshi died in September 1598. The Council of Five Elders ordered the remaining Japanese forces in Korea to retreat. Japan then initiated a series of policies called Sakoku to close Japan. It forbade Japanese to go abroad in ships, and initiated the death penalty for Japanese returning to Japan from abroad. This ended Japanese piracy definitively.

At the end of the 16th century, the Bunroku-Keicho War broke off the relationship between Korea and Japan. However, the Tokugawa shogunate started trading again with Korea by concluding the Treaty of Giyu with the So clan of Tsushima Island in 1609, establishing a relationship of near equality through mutual visits of Korean messengers. Tsushinshi were sent from Korea to pay homage to a new shogun or to celebrate the birth of an heir to a shogun. Korean envoys were provided with the same role as an envoy to bring tributes to a Chinese emperor or was used for showing the prestige of Tokugawa shogunate[citation needed].

In the 19th century, a severe conflict between at court between Heungseon Daewongun, the biological father of Gojong (king of the Joseon Dynasty), and Gojong's wife Queen Min continued. In 1882, Daewongun was seized by the Qing Dynasty China troops, and confined in Tianjin City (Jingo Incident). The Min family including Queen Min assumed authority, but relations between Japan and Korea did not turn better. Queen Min were changing their policies from pro-Japanese to Qing Dynasty China. In the Sino-Japanese War, When Japan beat China in 1895, the Treaty of Shimonoseki was concluded, and removed China's sovereignty Korea.[11] The Korea moved closer to Russia. Japan became alarmed when Russia enhanced its grip and influence over the Korean peninsula by acquiring vital state assets such as the mining rights in Chongsong and Gyeongwon sold off by Queen Min, timber rights in the north, and tariff rights, and purchased back and restored many of these. (The assassination of Queen Min occurred during this period).

In 1904, the Russo-Japanese War began, and Korea declared to be neutral. Japan conducted the Japan–Korea Treaty of 1904 immediately after the start of the war to eliminate restrictions in its military actions in the Korean Peninsula. Furthermore, the Japan–Korea Agreement of August 1904 was concluded in August, which brought the Korean government to receive Japanese financial and diplomatic advisors as well as to sit at the negotiating table for the conclusion of a treaty. After that, the Japan–Korea Treaty of 1905 was made, and Japan took over the diplomatic right of the Korean Empire, which practically made Korea the protectorate of Japan. However, Gojong, who did not accept the conclusion of this Treaty, dispatched secret envoys to the second Hague Peace Conference in 1907 in order to denounce the conclusion of the treaty as compulsive and invalid, but the trial failed and the Korea-Japan relationship deteriorated. On July 24, they concluded the Japan–Korea Treaty of 1907 to grasp domestic administration authority, and disbanded the army of the Korean Empire on August 1 immediately after that. Ito Hirobumi, who was the first prime minister of Japan and one of the elder statesmen and was Resident-General of Korea opposed to the annexation of Korea.[12] However, The power balance of the Japan domestic grew in favor of the annexation, because an influential statesmen group objecting to the early annexation disappeared due to the assassination of Ito Hirobumi by An Jung-geun in 1909. On August 22, 1910, annexing the Korea by signing the Japan-Korea Annexation Treaty.

The relationship between Korea and Japan is very complicated, because nothing has been conclusively agreed upon by historians, the differing interpretations of the same event will be divided for ease of understanding until the results of the joint history project between South Korea and Japan are used in both countries.

According to the announcement of South Korea, One conclusion of the joint history project was that Japan's interpretation of the 4th century was incorrect regarding Korea and Japan.[13] Currently, South Korea and Japan are trying to re-visit the joint history project which was halted due to differing focus points[14] "After conducting research for three years since 2002, scholars of the two countries announced their first report on three categories - the ancient, medieval, and modern times. At that time, Seoul demanded that the research institute’s findings be reflected in the textbooks of the two nations, but Japan rejected this request." Japan's refusal to use the research finding of the joint historians in Japanese schools caused South Korea to wonder why they were spending so much money researching history which wasn't going to be used in Japan. This event caused South Korea to halt the project in 2005.[13][14]

There are indications of cross-border political influence, but with varying accounts as to in which direction the political influence flowed. General consensus among Korean historians is that people who came from the continent through Korea to Japan became the ruling class of ancient Japan. Also, it is believed that the ruling class had close ties with Baekje, one of the three Korean kingdoms.[16] Buddhism was introduced to Japan from Baekje of Korea.[17][18][19][20][21][22][23][23][24] In 663, Japan, supporting Baekje, was defeated the allied forces of Tang China and Silla in the Korean Peninsula (the Battle of Baekgang), and the restoration of Baekje ended up in failure. Japan has had official contact with the Chinese since the 7th to 8th century.

From the early 13th–15th centuries there were a series of skirmishes by pockets of Japanese pirates on the Korean coast. During the Japanese invasions of Korea (1592–1598), many of Korea's cultural heritage was destroyed and looted by the invading Japanese armies. Although Korean land forces lost most of their land battles (with only a handful of notable exceptions), the Korean Navy won almost all the naval battles with decisive defeats of the Japanese fleet by Admiral Yi Sun-sin (who never lost a battle; the only battle Korean fleets lost to the Japanese was not commanded by Admiral Yi) cut off Japanese supply lines and helped drive the invading forces out of Korea. Among the atrocities of the Japanese soldiers was the practice of cutting off noses and ears of slain enemy soldiers, which evolved into cutting off those of the living and the civilians in order to fulfill the "kill quota" assigned to the troops. Hence the origin of the Korean saying to misbehaving children, "Ear-nose devils are coming!"[25] After the wars, Korean missions were dispatched 11 times to the Tokugawa shogunate of Japan between 1607 and 1811.[26]

With the erosion of Qing Chinese influences in the 19th century, Korea began to avoid Chinese influence, but also Western and Japanese control. Japan was rapidly modernizing in the second half of the 19th century and showing a keen interest in Korea, especially as it was the closest potential point of expansion directly on the Asian mainland. It was perceived that Japan would be vulnerable to any power that controlled the Korean peninsula. With the defeat of Qing forces in Korea in 1895, the murder of Empress Myeongseong by Japanese agents, and Japan's subsequent defeat of Imperial Russia in 1905, Korea came definitively under Japanese influence.

At the end of World War II, Korea regained its independence after 35 years of Japanese rule. Per the Yalta Conference agreements, Soviet forces accepted surrender of Japanese forces in northern Korea above the 38th parallel, and U.S. forces south of that line. Korea was then divided into Soviet (North Korean) and U.S. (South Korean) spheres. South Korea refused diplomatic and trade relations with Japan, using Japan as a domestic bugbear to rally support for the South Korean government. The early ROK(Republic of Korea; South Korea) government derived its legitimacy from its opposition to Japan and North Korea, portraying South Korea as under threat from the North and South. The diplomatic relationship between Japan and South Korea was established in 1965, when the Treaty on Basic Relations was signed; Japan subsequently recognized the Republic of Korea (the official name of South Korea) as the only legitimate government on the Korean Peninsula. As such, North Korea does not have official diplomatic ties with Japan.

^Watts, Jonathan (Dec 28, 2001). "The Emperor's New Roots". The Guardian. Retrieved 2012-06-11. "I, on my part, feel a certain kinship with Korea, given the fact that it is recorded in the Chronicles of Japan that the mother of Emperor Kammu was of the line of King Muryong of Paekche," [Emperor Akihito] told reporters.

^Metropolitan Museum of Art[6] "Metallurgy was also introduced from the Asian mainland during this time. Bronze and iron were used to make weapons, armor, tools, and ritual implements such as bells (dotaku)"

^A Brief History of the US-Korea Relations Prior to 1945. "While less than 100 Koreans in America enlisted in the US military during World War II, more than 100,000 Koreans served in the Japanese army as officers and soldiers. There were two Korean Lt. Generals in the Japanese Army: a Chosun prince, whose rank was honorary and who commanded no troops; and Lt. Gen. Hong Sa-Ik, who was a professional military man from the old Chosun army."